Weird problem with mate-screensaver

[Adam Funk]

Occasionally I come back to my computer to find a black screen that
cannot be unlocked because mate-screensaver had died before something
decided the computer was idle. The virtual consoles don't work, and
the only way I can get back in is ssh + `sudo service lightdm restart`
+ log in again --- obviously I lose whatever was running in the GUI.

I've figured out that I can prevent this by pressing ctrl-alt-L to
check that the screensaver appears, and if it doesn't I run
`mate-screensaver &` in a terminal --- then the screensaver works
normally. Unfortunately I don't always remember to do this, and
sometimes I don't know how long I'll be AFK.

I'm running Ubuntu-MATE 21.10 and version 1.26.0-0ubuntu1 of
mate-screensaver and mate-screensaver-common. The behavior in this
confirmed bug

<https://bugs.launchpad.net/ubuntu/+source/mate-screensaver/+bug/1947905>

sounds the same but I tried installing the older version
1.24.2-0ubuntu1 of those two packages for a week or two and had the
same problem.

Any ideas?

Thanks.